Card edge bus bar assembly for power distribution system

ABSTRACT

A bus bar assembly (110) includes a pair of source and return bus bars (118,116) mounted on at least one of the side edges (108,112) of a daughter card (102) and electrically connected by arrays of terminals (172) to power circuits of the card, for use in a system for distributing electrical power to the daughter card module (100) upon insertion into a card cage (10). The pair of bus bars (118,116) is insulated by a cover (120) having a rail (126) for following the guide channels (18,20) of the card cage at each card location. Rearward ends of the bus bars have blades (122,124) which are received into receptacle contacts (46,44) mounted in the card cage above and below the backplane (14), which are mounted at each card location and electrically connected to source and return busses (68,58) of the card cage, with the receptacle contacts (46,44) preferably being float mounted to be easily incrementally moved upon blade receipt during card module (100) insertion.

FIELD OF THE INVENTION

The present invention relates to the field of electrical connectionsystems and more particularly to the distribution of electrical power incard cage assemblies.

BACKGROUND OF THE INVENTION

Card cages are known which comprise a framework within which a pluralityof circuit panels or daughter cards are insertable, and within which isdisposed a backplane transverse to the back edges of the daughter cards.The upper and lower daughter card edges conventionally are disposedwithin upper and lower channels defined by the card cage framework andextending to selected positions along the backplane to define the cardposition within the card cage and to guide the card during insertioninto and removal from the card cage. Electrical circuitry of the cardsis connected to electrical circuitry of the backplane by any of severaltypes of known connectors and terminals, and is thereby interconnectedby the backplane to circuitry of other cards of the array and to otherelectrical components on the opposite side of the backplane.

Typically each daughter card in present commercial card cages receivesall necessary power for its components from the backplane through aplurality of terminals. One typical method involves providing amultilayer backplane having power-carrying circuit paths embedded withinit, involving significant fabrication expense, to which terminals areengaged to transmit the power at current levels, ordinarily of about oneampere per terminal, through connectors to the daughter card. Connectorswhich must house the quite numerous power-carrying terminals also musthouse signal terminals for the primary purpose of providing signaltransmission to and from the daughter cards; signal terminals are thuslimited in number and in their position, which in turn limits thecapabilities of the daughter cards. Also, the current levels presentlyavailable limit the number and types of components usable with thedaughter cards.

One approach to distribute power to daughter cards in an improved manneris disclosed in U.S. Pat. No. 4,846,699 in which the power is providedto upper and/or lower edges of each daughter card rather than along theback edge. The upper and/or lower guide channels are defined by elongateelectrical connectors containing a plurality of electrical terminalswhich are movable into and out of engagement with corresponding contactlocations along the card by an actuation system within each connector.The plurality of terminals thus distributes electrical power to discretelocations and discrete power circuits on the card. Thus during cardinsertion and removal the contact sections of the terminals areretracted from the guide channel and would not engage any portions ofthe card nor interfere with insertion and removal of a card; only whenthe cards have been fully inserted and locked into position are theterminals moved into electrical engagement with the contact means alongthe card edge. Examples of such zero insertion force connectors areparticularly disclosed in U.S. Pat. No. 4,789,352 and No. 4,834,665.With such connectors, conductors such as flat cables are needed to berouted through the card cage framework above and below the daughtercards and electrically connected to the terminals of the connectors andto a power supply for the card cage.

It is desired to provide a power distribution system for daughter cardsof a card cage which utilizes a portion other than the back edge of eachcard for transmitting power to the card, without interfering withinsertion or removal of the card.

It is desired to provide such a system which minimizes the amount ofdaughter card real estate utilized for receipt and return of power whileretaining the benefits attained by a substantial plurality of powerconnecting sites.

It is additionally desired to provide a power distribution system whichelectrically connects with the card upon insertion and disconnects uponcard withdrawal.

It is also desired to provide such a system which does not require aplurality of cables routed throughout the card cage.

It is further desired to provide such a system which would provide powerto each card at substantially increased levels without significantvoltage drop.

It is further desired that such a power distribution system not obstructforced air flow between adjacent daughter cards in the card cage, neededfor cooling.

SUMMARY OF THE INVENTION

The power distribution system of the present invention includes a pairof bus bars mounted to at least one of the upper and lower edges of adaughter card, with an insulator thereover. Each bus bar includes flangeportions coextending inwardly along the corresponding card edge andincludes a plurality of contact terminals secured to the bus bar andextending into plated through-holes into the card for electricalconnection to power circuitry of the card. At the rearward ends of thebus bars are blade-shaped contact sections extending further rearwardlybeyond the card's rear edge. Mounted to the framework at the rear of thecard cage are upper and/or lower assemblies of pairs of receptaclecontacts at each daughter card location and electrically connected to apower bussing system of the card cage having source and return paths,the receptacle contacts of each pair being associated with each bus barof a daughter card to be inserted and matable with the blade-shapedcontact section of the respective bus bar and comprising a separableinterface. One of each pair of bus bars may be a source path and theother a return path, and preferably the blade-shaped contact section ofthe return path bus bar is longer to engage its respective receptaclecontact first during card insertion and disengage last upon cardwithdrawal. The system is disclosed in U.S. patent application Ser. No.07/546,335 filed Jun. 29, 1990 (AMP Case. No. 14832) filed assigned tothe assignee herewith.

According to the present invention, the bus bars include elongate bodysections having several flanges extending therefrom; the bus bars are oflow resistance conductive metal and have a substantial mass because oftheir substantial current-carrying cross-section. The bus bars can beassembled together with insulation between their body sections, suchthat their flanges are laterally offset from the body sections andalternate with and are slightly spaced from each other along the bus barlength. Mounting of the bus bars to the card edge can be assuredlyattained through the use of a plurality of compliant pin terminals whichare firmly secured within holes through the bus bar flanges along thelength of each bus bar and also firmly secured within correspondingthrough-holes along the card edge, and preferably are of the type havinga pair of compliant sections as disclosed in U.S. Pat. No. 4,186,982.The compliant pin terminals also establish the substantial plurality ofelectrical connections to the card power-carrying circuitry along thecard edge, for transmitting power to a substantial plurality of cardsites considered necessary for effective power distribution. The busbars may have several flange sections alternating with the flangesections of the other bus bar and having their card-proximate surfacesin a common plane to face a common surface of the card, and thecompliant pin terminals may coextend in two rows into the card from acommon side, facilitating assembly The compliant pin terminals beingdisposed in two spaced rows significantly resists damage to the cardfrom torque resulting from lateral stress on the bus bars.

The present invention may be used with receptacle contacts such as ofthe type disclosed in U.S. Pat. No. 4,845,589 and include a receptaclecontact section including a lead-in defining a capture range formatingly receiving thereinto a blade-shaped bus bar contact section,which has been substantially aligned therewith by guides of the cardcage followed by rails of the daughter cards during card insertion. Eachhas a plurality of opposed spring arms of substantial spring strengthestablishing a contact normal force of about four pounds per spring arm,required to establish assured low resistance electrical connections forthe transmission of power, for instance at 75 amperes.

Since the card edge connectors along the back edge of the card contain asubstantial plurality of signal terminals small in size and closelyspaced, it is crucial that the connectors which house them are preciselyaligned with the mating connectors mounted to the backplane at leastjust before the signal terminals matingly engage. Alignment posts of thebackplane connectors can enter post-receiving holes of the card edgeconnectors in order to incrementally adjust the position of the cardedge connectors, provided that the power distribution system does notinterfere with the incremental adjustment movement of the card's rearedge to conform the position of the card edge connectors to thebackplane connector alignment posts. The effect of the substantialmechanical gripping of the blade-shaped sections by the receptaclecontacts on the card edge adjustment, is minimized by mounting thereceptacle contacts in a manner permitting floating thereof with littlemechanical resistance of the type which would otherwise occur were thereceptacle contacts to be rigidly mounted and the stiff spring arms tobe even further deflected.

The receptacle contacts used with the present invention may be of thetype disclosed in U.S. patent application Ser. No. 07/546,620 filed Jun.29, 1990 and assigned to the assignee hereof. The receptacle contactsare loosely mounted along a shaft secured within a castellated clevisblock permitting rotation therearound in a vertical plane parallel to adaughter card. Each receptacle contact is mounted in a loose fit betweena respective pair of salients of the clevis block which combined with aloose fit with respect to the shaft permit float in two orthogonaldimensions to a limited extent sufficient to accommodate all adjustmentmovement of the card edge. Each receptacle contact may be assuredlyconnected to the power bussing system of the card cage by acorresponding rearward receptacle contact section gripping a respectiveblade-shaped section of the source or return card cage bussing meanswith substantial contact normal force, which provides the location aboutwhich the receptacle contact pivots when moved incrementally by theblade-shaped contact section of the source or return bus bar uponinitial engagement during card insertion, and then incrementally by thecard edge alignment system. Thus the assembly of receptacle contacts tothe clevis block provides a floating separable interface, with therespective receptacle contacts permitted to move in two orthogonaldirections (which define a plane parallel to the backplane)independently of each other while still gripping in the third or axialdimension the opposed blade-shaped contact sections of the card cagebussing system and the bus bars of the daughter cards. Thus theincremental adjustment movement essentially does not encounterresistance from needing to deflect the stiff spring arms of thereceptacle contacts nor friction resistance from needing to move theblades along the arrays of opposed spring arms gripping them.

It is an objective of the present invention to provide a system fordistributing electrical power to a substantial plurality of sites alongthe upper and/or lower edge of a daughter card, electrically connectablewith bussing means of the card cage upon card insertion.

It is also an objective for the power connections of the system bematable and separable automatically during card insertion andwithdrawal.

It is also an objective that such a power distribution system engageprior to signal connections being established between the daughter cardand the backplane, and further that the return power circuit beestablished prior to the source power circuit.

It is additionally an objective that the two electrical connectionsalready established during the intermediate stage of card insertion,each sufficient for transmitting 75 amperes, not interfere with theincremental adjustment in card edge position necessary at the finalstage of daughter card insertion to precisely align the multitude ofsignal terminals in the high density card edge connectors withcorresponding terminals of the back plane connectors.

It is a further objective that the bus bars of substantial mass besecured and electrically connected to a respective card edge in anassured manner and in a manner which minimizes the effects of torque onthe card edge without necessitating mounting hardware nor heat, flux,solder nor adhesives in order to simplify card fabrication and assemblyof the bus bars to the card edge.

It is an additional further objective that the bus bar assemblies fordaughter cards be essentially independent of variations in cardthickness in a large range of possible thicknesses, such as between0.085 and 0.25 inches.

It is also a general objective that the power distribution system of thepresent invention minimize the voltage drop through all the electricalconnections between the cage bussing system and the daughter card powercircuits.

It is additionally an objective that the power distribution system andespecially the bus bar assemblies not obstruct forced air flow betweenthe daughter cards for cooling purposes.

An example of the preferred embodiment of the present invention will nowbe described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a card cage having a backplane andlocations for a plurality of daughter cards, and a daughter card forinsertion thereinto, having the power bussing system of the presentinvention;

FIG. 2 is an isometric view of a card in position in its guide channelsof the card cage of FIG. 1 showing the power distribution system;

FIG. 3 is an enlarged portion of two card modules in the card cage ofFIGS. 1 and 2 showing the separable interface of the power distributionsystem, with blade contact sections of the buses of a card moduleassociated with float-mounted receptacle contact members of the cardcage bussing system, and showing a card edge connector along the rearedge of a card module and an associated backplane connector;

FIGS. 4A, 4B, and 4C are diagrammatic illustrations of an upper edge ofa card module having a bus bar assembly mounted therealong, in severalphases of insertion into a card cage and showing mating of the bus barcontact sections occurring prior to mating of the card and backplaneconnectors, with an alignment system shown;

FIGS. 5, 6 and 6A show a bus bar assembly for a card edge, prior toassembly and fully assembled to be mounted onto a card edge, with FIG.6A being an enlarged view of a portion of a bus assembly showing aninsulator retained over the bus bar pair;

FIG. 7 is an enlarged view of a flange of a bus bar with strips ofcompliant pin terminals to be mounted thereinto;

FIG. 8. is a representative section view of a portion of a card moduleedge having a bus bar assembly mounted therealong, showing severalcompliant pin terminals mechanically securing and electricallyconnecting the bus bar to the card;

FIG. 9 is an isometric view of a clevis block and representativereceptacle contact therefore prior to assembly together, and showing themounting shaft and a bushing;

FIG. 10 shows the receptacle contact block fully assembled and alsoshowing the associated power bussing system of the card cage to which itwill be connected upon mounting in the card cage;

FIGS. 11A to 11D diagrammatic illustrations in plan view of a bus barassembly of a card module during a mating sequence, showing the floatingnature of the receptacle contacts of the block of FIG. 10 in response tothe first blade and the second blade in FIGS. 11A and 11B, theengagement of the alignment system of the card edge and backplaneconnectors in FIG. 11C, and the card fully inserted and fully connectedin FIG. 11D.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The power distribution system with which the present invention isespecially utile, is disclosed in U.S. patent application Ser. No.07/546,335. A card cage 10 as in FIGS. 1 and 2 includes a framework 12,a backplane 14 on which are mounted a plurality of vertically disposedhigh density backplane connectors 16 corresponding to daughter cardlocations, and a plurality of pairs of upper and lower guide channels18,20 defined in guide members 22,24 extending forwardly from backplaneconnectors 16 at the card locations to leading ends 26,28 at front face30 of the cage 10. A representative daughter card module 100 includes adaughter card 102 having a rear edge 104 on which is mounted a singlehigh density card edge connector 106 (or series of connectors). Alongupper edge 108 of card module 100 of FIG. 1 is mounted a bus barassembly 110, and along lower edge 112 is mounted a similar bus barassembly 114. Each bus bar assembly includes a pair of first and secondbus bars 116,118 (see FIGS. 5 and 6) covered by an insulator 120. Atrearward ends of bus bar assemblies 110,114 are first and secondblade-shaped contact sections 122,124 of the first and second bus bars116,118 which extend outwardly from insulator 120 and rearwardly of rearcard edge 104 and card edge connector 106.

Insulator 120 of each bus bar assembly 110,114 includes a rail 126 tofollow guide channels 18,20 during card insertion. To assure that thecard module is appropriately oriented, polarization may be provided bythe depth of upper guide channel 18 being greater toward one side at 19and the depth of lower guide channel 20 being greater toward the sameside at 21; correspondingly the upper rail 126 would then include anoffset narrow flange portion 128 toward that side after appropriatemounting and the offset narrow flange portion 128 of the lower railwould be positioned toward that same side after appropriate mounting sothat the narrow rail flange portions 128 would prevent a daughter cardmodule 100 being inserted in the improper inverted orientation whereinthe rail flange portions would occur on the opposite side of the guidechannels from the side of deeper channel portions 19,21. Otherconfigurations of complementary rail/channel engagement geometries arepossible, where the cross-section geometries of the upper and lowerrail/channel systems are asymmetric between left and right sides toassure proper orientation of the daughter card during insertion; it ispreferred that the geometries required of the upper and lower insulators(and likewise the upper and lower guide members) be mirror imageopposites in cross-section so as to permit manufacture thereof by acommon extrusion, and then be mountable in opposed orientations.

Card module 100 includes mounted pivotably along front edge 130 aninsertion/ejection member 132 at the forward end of upper edge 108 andanother such insertion/ejection member 134 at the forward end of loweredge 112, each of which includes a catch-receiving slot 136 cooperablewith respective catches 32,34 of the card cage framework 12 to assistfinal stages of card module insertion. Insertion/ejection members132,134 are mounted to daughter card 102 by pivot pins 144 extendingthrough apertures of the card and through both tines of aperturedclevises 146. Insertion/ejection members 132,134 are provided withelongate handles 138 movable flush to the daughter card forward edge130; members 132,134 assist completion of card module insertion byproviding mechanical advantage to overcome the resistance to bus bar andconnector mating, and to retain the card module in position and also toinitiate first stages of card module disengagement during withdrawal andremoval. Catches 32,34 may be rods mounted transversely through leadingends of guide members 22,24. Also shown within the card cage 10 areupper and lower power bus assemblies 36,38, and forwardly thereof arereceptacle contact blocks 40,42.

FIG. 2 illustrates card module 100 in a fully inserted position withincard cage 10, showing both bus bar assemblies 110,114 in matedengagement with respective pairs of receptacle contacts 44,46 of upperand lower receptacle contact blocks 40,42. Blade contact sections116,118 have been received into receptacle contact sections 48,50 (FIG.3) of receptacle contacts 44,46 each having a plurality of spring arms52 opposed in pairs, the spring arms 52 having substantial springstrength. The backplane 14 of the card cage has been removed to show allof the essential portions of the separable interface of the powerdistribution system of the present invention from the bus bar assemblyto the card cage bussing system.

In FIG. 3 is shown an enlargement of the lower separable power interfacedefined by the bus bar blade contact sections of lower bus bar assembly114 and the receptacle contact sections 48,50 of contacts 44,46 mountedin lower block 42, with only blade contact section 122 of the return busshown. The separable interface is mounted to framework 12 and disposedbelow the lower edge of backplane 14, and receptacle contact sections48,50 extend forwardly of backplane 14 for early engagement with bladecontact sections 122,124. Also shown is the rearward receptacle contactsection 54 of a receptacle contact 44 mated with a blade-shaped contactsection 56 of return bus member 58 of lower power bus assembly 38.

On backplane 14 is seen a lower portion of high density backplaneconnector 16 within which are secured a multitude of electrical signalcontacts (not shown) which will mate with corresponding signal contacts(not shown) in card edge connector 106 mounted along rear edge 104 ofdaughter card 102. In order to assure that the plurality of matingsignal contacts of the mating connectors will mate properly, analignment system is provided comprising of for example several alignmentposts 80 spaced along and solidly mounted to each backplane connector 16and/or to backplane 14 and precisely located with respect to the signalcontacts of the connector. The alignment posts 80 cooperate withpost-receiving apertures (FIGS. 11A to 11D) of card edge connector 106which apertures are similarly precisely located with respect to the cardedge connector terminals. The engagement of the leading ends ofalignment posts 80 with bearing surfaces of the aperture entrances(FIGS. 11C and 11D) urges the card edge connector (and the card moduleto which it is affixed) to adjust its position to be precisely alignedwith the backplane connector, which could involve incremental movementvertically or horizontally or both as the card module 100 continues tobe urged forwardly into card cage 10 along upper and lower guidechannels 18,20.

Referring now to FIGS. 4A to 4C, the mating sequence of card module 100into card cage 10 is depicted in diagrammatic form and shows the upperbus bar assembly 110 mating with the upper separable interface comprisedof upper receptacle contact assembly 42 and upper bus assembly 36 of thecard cage. Receptacle contact member 44 is shown including an insulativebushing 60 extending through body section 62 and mounted on shaft 64 ofclevis block 66 in upper contact assembly 42. Upper bus assembly 36includes return bus member 58 and source bus member 68, with anappropriate insulation layer 70 therebetween; rearward receptaclecontact section 54 of contact member 44 is mated onto blade-shapedcontact section 56 depending from contact member 72 affixed to returnbus member 58 and extending forwardly therefrom. Blade-shaped contactsections 74 similarly depend from contact members 76 affixed to sourcebus member 68 (FIG. 10) in each of upper and lower bus assemblies 36,38,arranged so that sections 74 extend upwardly to alternate with sections56 extending downwardly to define a common row of blade-shaped contactsections for the array of rearward receptacle contact sections ofcontact assemblies 40,42.

In FIG. 4A card module 100 has been inserted most of the way into cardcage 10 with rail 126 guided within guide channel 18 of guide member 22,and insertion/retention member 132 is oriented about pivot pin 144 intoposition A for catch 32 to abut arcuate engagement surface 140 forwardlyof slot 136. Also seen is an insulative end cover member 148 similarlymounted by pivot pin 144 insulating the ends of the bus bars.Blade-shaped contact section 122 of the return bus bar extendsrearwardly toward forward receptacle contact section 48 of contactmember 44 to be received between opposed pairs of spring arms 52.Shorter blade-shaped contact section 124 of source bus bar is shown inphantom behind blade-shaped contact section 122. Card edge connector 106on rear edge 104 of card 102 faces and is spaced from correspondingbackplane connector 16 mounted on backplane 14, and one of the severalalignment posts 80 for backplane connector 16 is shown extendingforwardly theretowards.

In FIG. 4B insertion/ejection member 132 has been lowered to position Bso that tine 142 opposed from arcuate engagement surface 140 is raisedalong the inside surface of catch 32 and bearing thereagainst, thusurging card module 100 further inwardly. The leading blade edge ofblade-shaped contact section 122 has entered the lead-in defined by thediverging spring arm free ends of spring arms 52 of forward receptaclecontact section 48 and has deflected the spring arms of the opposingpairs apart and entered therebetween meeting and overcoming substantialresistance to mating. Second, shorter blade-shaped contact section 124will shortly thereafter similarly mate with corresponding forwardreceptacle contact section 50 again meeting and overcoming substantialresistance to mating, as insertion/ejection member 132 is moved furthertoward front card edge 130. Alignment post 80 approaches card edgeconnector 106 to begin its precision alignment function.

In FIG. 4C full card module insertion has been attained, withinsertion/ejection member 132 in final position C along front card edge130. The blade-shaped contact sections of both bus bars have been fullymated with respective receptacle contact sections. Alignment post 80 ofbackplane connector 16 has entered the corresponding aperture of cardedge connector 106 and aligned the card edge connector with thebackplane connector, and mating thereof has occurred with all pairs ofmating terminals having been precisely aligned and mated.

Referring to FIGS. 5 to 8, the portions of bus bar assembly 110 for cardmodule 100 are illustrated, and assembly thereof will now be described.Return bus bar 116 includes first blade-shaped contact section 122extending therefrom, longer than second blade-shaped contact section 124extending from source bus bar 118. Both contact sections 122,124 areoffset a distance apart to mate with similarly spaced apart forwardreceptacle contact sections 48,50 of receptacle contact assembly 42 andinclude blade-like double beveled leading edges to facilitate matingtherewith. Bus bars 116,118 are affixed together with a layer ofinsulative material 158 therebetween.

Bus bar 116 includes a plurality of flanges 150 alternating withrecesses 152 and offset from the bus bar side surface toward bus bar 118a distance equal to half a flange thickness plus half the thickness ofinsulative layer 158; bus bar 118 similarly includes a plurality offlanges 154 alternating with recesses 156 and offset toward bus bar 116.The flanges of each bus bar are located opposed from respective ones ofthe recesses of the other bus bar, and all flanges and recesses areshaped and dimensioned so that when the bus bars are affixed togetherwith a layer of insulation 158 therebetween, the flanges of both definea common row specifically to define substantially a common plane ofcard-facing surfaces 160,162. Side edges of each flange are spaced fromopposing side edges of adjacent flanges a precise amount for electricalisolation at spacings 164 which may be about 0.045 inches widesufficient for voltage levels of the 5 to 10 volt range commonly desiredin card cage power applications. The embodiment shown includes fourflanges each about 1 inch long; however the number of flanges and theirlength can be modified as desired.

In FIG. 6A is shown one manner of retaining insulator 120 on a bus barassembly: the flange-covering section 194 of the insulator isultrasonically deformed at least one spacing 164 between flanges 150 and154 so that a portion 196 of the insulator material is now embeddedtherebetween preventing axial insulator movement. Another manner ofinsulator securement optionally could comprise or include insulativemember 148 (FIG. 4A) mounted to the daughter card at the front edge 130at each insertion/ejection member 132,134 by the same pivot pin 144 bywhich the insertion/ejection member 132,134 is mounted. The corners ofthe insulator could be rounded if desired to facilitate forced air flowtherearound.

In each flange 150,154 of both bus bars 116,118 are preferably two rowsof pin-receiving apertures 166 to receive thereinto respective compliantsections 170 of first sections 172 of pin terminals 174. Pin terminals174 are preferably stamped and formed on carrier strips 176 and retainedthereon during assembly and thereafter. As seen in FIG. 8, carrierstrips 176 extend integrally from central terminal sections 178 betweenfirst compliant sections 170 and second compliant sections 180 on secondterminal sections 182. First compliant sections 172 are gripped withinappropriately dimensioned apertures 166, thereby requiring at leastabout five pounds axial pushout force on each terminal for extraction.When bus bars 116,118 have each been fully loaded with compliant pinterminals 174, they are secured together so that second terminalsections 182 coextend outwardly from card-facing surfaces 160,162 offlanges 150,154.

Bus bar assembly 110 is applied to the reference surface side of cardedge 108 by insertion of the plurality of second terminals sections 182into respective through-holes 184 arrayed in two rows in each ofalternating regions 186,188. Second compliant sections 180 are grippedby the wall surface of through-holes 184, thereby requiring at leastabout five pounds axial pushout force one each terminal for extraction.Compliant sections 172,182 are preferably of the type disclosed in U.S.Pat. No. 4,186,982 which can establish such substantial levels of forcethat assured mechanical and electrical connections are made by theterminals to the substrate without solder or any additional retentionmechanism. Thus with a plurality for example of 92 terminals for eachbus bar (23 per flange, in rows of 12 and 11 each) a total of 184terminals having the specified type of compliant section is sufficientto establish that an aggregate force of at least about 900 pounds wouldbe required to remove each of the bus bar assemblies 110,114. While suchexcellent retention force is defined by the particular compliant pinterminals disclosed, other mounting means such as bolts may be used forbus bar mounting if other types of terminals were to be used. Toolingand apparatus is in commercial use which can apply the necessary forceof less than forty pounds per pin terminal, or in other words a maximumtotal of about 7500 pounds to apply each bus bar assembly to thedaughter card.

In the embodiment shown, the carrier strips 176 define a selectedspacing between the flanges and the card surface, and also serve toretain the terminals precisely spaced during assembly and to act as astop mechanism to assure all pin terminals inserted to a common desireddepth. The two-row array of terminals resists damage to the card edgefrom torque which may inadvertently be applied by the bus bar assembly;there is no one row of terminals which by itself would act to define apivot point tending to permit rotation of the bus bar assembly about therow and thereby damage the card and the terminals; further the pluralityof through-holes are now spaced farther apart than the same number wouldbe spaced within a common row, allowing more card structure between theholes. Where the spacing of through-holes 184 cannot be positioned withabsolute precision to correspond with the positioning of the terminalson a carrier strip, the compliant pin terminals may be separate from acarrier strip upon insertion.

The plurality of terminals extending from each flange to a respectivethrough-hole region of the card edge define a plurality of distinctelectrical connections therebetween dividing the current from the busbar flange to a plurality of hole locations on the card, thusefficiently distributing the current to a substantial plurality of siteswithout exceeding the nominal capacity of individual terminals, andsimilarly efficiently gathering the return current. The carrier stripscommon the terminals after their receipt of the current by the firstterminal sections of the row of terminals of the source bus bar (or byreceipt from the second terminal sections of the return bus bar), andredistribute it to the second (or first) terminal sections, thuscompensating for a single less-than-optimum electrical connection at oneof the first or the second compliant sections of one of the terminals ofa row. Distribution of Joule or resistive heating from theterminal/board interface is also assisted by the carrier stripconducting heat from individual terminals.

The card can be customized to transmit the current received by eachthrough-hole to an embedded power plane which may intersect allthrough-holes of the region and then conduct the current elsewhere onthe board to components such as representative integrated circuitdevices 192 in FIG. 6. The compliant pin terminals and the mountingmethod disclosed accommodates different board thicknesses of from about0.085 to 0.250 inches or more and is also forgiving of manufacturingtolerances in card thickness. Such essential independence from boardthickness permits existing card cage systems having the powerdistribution of the present invention, to be upgraded withoutmodification with new card modules having the bus bar assembly of thepresent invention, but having daughter cards of different thicknessesthan the ones they replace.

The card may also utilize elevated bus bars of the type disclosed inU.S. Pat. No. 4,869,673 which will extend from the card edge to theinterior regions of the card's major surfaces thus essentially freeingup the major surface for use by signal circuits and components only, andsimplifying card fabrication by eliminating the need for multilayeredconstruction for embedding power circuitry within the card. Appropriateelectrical connections can be provided from the through-holes to contactsections of the elevated bus bars near the card edge by surface orembedded card circuitry; it is also possible to utilize compliant pinterminals to interconnect the bus bar flanges directly to tabs on theelevated bus bars, with other mounting means such as bolts provided toaffix the bus bar assembly to the card edge.

Bus bars 116,118 can be extruded for example of low resistance copperalloy such as Alloy No. C110 and then flanges 150,154 formed from aninitially continuous flange portion to define recesses 152,156;blade-shaped contact section 122,124 can then be formed, then annealedto half hard temper and thereafter plated with nickel underplating andthen silver plating followed by application of a tarnish resistantcoating. It may be desirable to extrude both bus bars from adjacentportions of the same copper alloy extrusion to best assure an identicalthickness, which may be about 0.187 inches. Pin-receiving apertures 166of appropriate diameter such as 0.040 inches can be machined intoflanges 150,154; the spacing between apertures of a single row may be0.100 inches, and the rows may be spaced 0.065 inches apart; thethrough-holes of daughter card 102 would be identically spaced withineach region and have identical diameters of 0.040 inches after plating.

Compliant pin terminals 174 can be stamped from a continuous strip ofstock copper alloy such as Alloy No. C260 and having generally arectangular cross-section of 0.025 by 0.034 inches, but with thediagonal across each compliant section 170,180 of about 0.050 inches toassure the desired substantial gripping force upon being reduced duringinsertion into flange apertures 166 and through-holes 184 respectivelyfrom 0.050 to 0.040 inches. Insulator 120 may be extruded for examplefrom a thermoplastic such as nylon and have a shape conforming snugly tothe outer shape of the bus bars affixed together and also include aflange-covering section 194 as well as rail 126, with polarizing railflange portions 128 easily extruded Insulator 120 may be inserted overthe bus bar assembly before mounting to the card edge to facilitatehandling of the bus bar assembly as a unit during card mounting, andthen secured. Insulating layer 158 may be for example 0.005 inch doublesided tape such as of MYLAR or KAPTON.

The components of receptacle contact assembly 40 (or 42) are shown inFIGS. 9 and 10, as disclosed in U.S. patent application Ser. No.07/546,620. Each receptacle contact member 44 (or 46) includes a bodysection 62 having a hole 82 therethrough within which is secured aninsulative bushing 60. A shaft-receiving hole 84 is formed throughbushing 60 through which extends shaft 64. Clevis block 66 includes aplurality of salients 86 spaced therealong through each of which is ashaft-receiving aperture 88, and contact-receiving recesses 90 aredefined between salients 86 and having controlled widths greater thanthe width of body sections 62 of contact members 44. Shaft 66 may beretained in the assembly by a pair of locking clips inserted on endsections extending from the clevis block and having annular recessestherearound; clevis block 66 preferably has mounting flanges 92 forbeing mounted to the card cage framework.

Each receptacle contact is preferably stamped from low resistance stockalloy such as Alloy No. C151 having a thickness of 0.062 inches forexample, and then formed to have arrays of spring arms 52 in bothforward and rearward receptacle sections 48,54, each spring arm havingan angled free end The contact is then formed so that body section 62 isrectangular in cross-section and so that the spring arms of each contactsection oppose each other a precise selected distance apart of forexample about 0.120 inches at blade-engaging arcuate constrictions atthe bases of now-diverging opposed angled free ends together now actingas a lead-in and defining a capture region for receipt of a slightlymisaligned blade front end during mating. Since the forming of bodysection 62 involves abutting the free ends of the blank along a seam,the free ends must be locked together by a locking system such as thedovetail arrangement 78 wherein a tab is locked into an undercut groovesimilar to that disclosed in U.S. Pat. No. 4,932,906; the locking systemassures that all opposed spring arms sustain equivalent and appropriatecontact normal force upon deflection during mating with a correspondingblade. The entire contact member may be plated with nickel underplatingand silver plating as desired for terminals conducting substantialcurrent levels. Receptacle contact sections 48 and 54 are preferred tobe similar to that disclosed in U.S. Pat. No. 4,845,589. Clevis block 66may be molded for example of thermoplastic such as acetal resin, andshaft 64 may be a steel rod; insulative bushings 60 may be molded ofthermoplastic such as nylon.

Receptacle contact assembly 42 is shown fully assembled in FIG. 10, inassociation with power bus assembly 38. Power bus assembly 38 includessource bus member 68 and return bus member 58 having insulation 70therebetween. Contact members 72,76 may be formed from low resistancecopper alloy like Alloy No. C110 about 0.187 inches thick, annealed tohalf hard temper if desired, and nickel underplated and silver platedand followed by application of a tarnish resistant coating. Contactmembers 72,76 are mounted to respective ones of bus members 58,68 sothat blade-shaped contact sections 56,74 respectively alternate witheach other opposed from respective rearward receptacle contact sections54 of receptacle contact members 44,46 of assembly 42. Power bus members58,68 may be extrusions of copper alloy such as Alloy C110 withflange-receiving recesses and mounting apertures formed thereinto inorder to be secured such as by conventional hardware to an insulativesupport 94 such as of thermoplastic acetal or glass-filled polyesterresin in order to be mounted to the framework of the card cage.Insulation 70 may be 0.03 inch thick glass-filled epoxy. Receptaclecontact assembly 42 is also mounted to the card cage framework forwardlyof the associated power bus assembly, with rearward contact sections 54mated with appropriate associated ones of blade-shaped contact sections56,74 under substantial contact normal force such as about four poundsper spring arm.

The incremental aligning capabilities of the mating of the bus barassemblies 110,114 of card module 100 with the separable interfacedefined by receptacle contact assemblies 40,42 and also the criticalafter-mating adjustability thereof, will now be described with referenceto FIGS. 11A to 11D, and with reference to FIGS. 4A to 4C. FIGS. 11A to11D illustrate diagrammatically in plan view an upper bus bar assembly110 of card module 100 approaching an upper contact assembly 40 matedwith upper power bus assembly 36 of card cage 10, with a backplaneconnector 16 opposed from a corresponding card cage connector 106 onrear edge 104 of card 102 of card module 100; one of the severalalignment posts 80 of backplane connector 16 is opposed from acorresponding post-receiving aperture 196 in card edge connector 106.

In FIG. 11A a lower guide member 24 of cage framework 12 is visibleforwardly of backplane 14 and has a guide channel 20 approximatelyaligned with backplane connector 16 and alignment post 80 thereof. Firstblade-shaped contact section 122 of return bus bar 116 is opposing andis approximately aligned with a corresponding receptacle contact member44, while second blade-shaped contact section 124 of source bus bar 118is opposing and is approximately aligned with a corresponding receptaclecontact member 46; the forward receptacle contact sections 48,50 thereofextend forward of backplane 14 above an upper edge thereof.

Receptacle contact members 44,46 are mounted to clevis block 66 on shaft64 thereof Recesses 90 between salients 86 of clevis block 66 areslightly larger than the width of body sections 62 of members 44,46permitting limited side-to-side movement and angular movementtherebetween. Insulative bushings 60 through body sections 62 (FIG. 9)have shaft-receiving holes 84 with inside diameters slightly larger thanthe outer diameter of shaft 64, thereby permitting limited angular orskewing movement of each receptacle contact member as well as rotationalmovement about the shaft, all generally pivotable about the grippingengagement of rearward receptacle contact sections 54 onto blade-shapedcontact sections 56,74 of power bus contact members 72,76. Thusreceptacle contact assembly can be said to define a floating separablepower interface while still firmly mechanically and electricallyconnected to contact members of the power bus assembly of the card cage,with forward receptacle contact sections possessing limited movementcapability in any direction in a plane parallel to the backplane.

In FIG. 11B the front end of first blade-shaped contact section 122 hasentered the lead-in of receptacle contact section 48 and has deflectedapart the opposing spring arms 52 thereof, overcoming a peak insertionresistance of about eight pounds, while easily incrementally adjustingthe position of the forward end of receptacle contact section 48 ifnecessary. Second blade-shaped contact section 124 is approachingreceptacle contact section 50; card edge connector 106 is approachingbackplane connector 16.

In FIG. 11C the front end of second blade-shaped contact section 124 hasentered the lead-in of receptacle contact section 50 and has deflectedapart the opposing spring arms 52 thereof, overcoming a peak insertionresistance of about eight pounds while easily incrementally adjustingthe position of the forward end of receptacle contact section 50 ifnecessary, simultaneous with first blade-shaped contact section 122being urged farther into receptacle contact section 48 against afriction resistance of about four pounds. Card edge connector 106 hasbeen moved adjacent backplane connector 16, with the leading end 96 ofalignment post 80 about to enter post-receiving aperture 196 at theentrance 198 defined by a chamfered lead-in.

In FIG. 11D leading end 96 of alignment post 80 has engaged the lead-insurfaces of aperture entrance 198 and has urged the card edge connectorincrementally at least laterally (and commonly vertically as well),necessarily also urging the entire rear edge 104 of card module 100simultaneously, as well as the bus bar assemblies 110,114. During theincremental adjustment movement, the blade-shaped contact sections122,124 of both bus bar assemblies also must necessarily move; thefloating separable interface defined by receptacle contact assemblies40,42 are adapted to permit such movement of already-mated blades andreceptacles with acceptably low mechanical resistance over and abovesimple inertia.

Therefore, incremental adjustment of the rear card edge 104 in thehorizontal direction is accomplished without having to overcome thestiff spring arms of one side of each of the four receptacle contactsections 48,50 mated with the four blade-shaped bus contact sections122,124. The aggregate mechanical resistance by the arrays of springarms of the four receptacle contacts would have been up to about fourpounds per mil for horizontal movement. With the present invention thisstiffness (plus friction from blade/finger wiping during incrementalpivoting) is reduced to about 0.01 pounds per mil. For example, wherehorizontal adjustment movement might require a horizontal translation oftwenty mils, the total mechanical resistance would have been eightypounds, whereas such horizontal translation in the present embodiment ofthe present invention would encounter a total mechanical resistance ofabout 0.20 pounds, plus a certain additional resistance due to frictionas portions of the insulative bushings may bear somewhat againstportions of the smaller-diameter shaft in the clevis block.

Adjustment movement is accomplished in the vertical direction withouthaving to overcome the full friction resistance of the spring armsgripping the blades in order to move the blades relative to the springarms. The aggregate friction resistance would have been up to aboutsixteen pounds for vertical movement; with the present embodiment of thepresent invention this aggregate friction resistance is reduced to aboutthree pounds. Overcoming the deflection resistance of the spring armsand the friction resistance of the spring arms with respect to theblades would otherwise be necessitated were the receptacle contactmembers to be fixed mounted, and would have prohibitively stressed theprecision alignment mechanism of the backplane and card edge connectors.

The power distribution system of the present invention permits poweringof a daughter card module as a result of card insertion, where the poweris brought to the side edges rather than the rear edge, thus freeing upall rear edge locations for signal connections with the backplane.Higher levels of power can be transmitted to the card than withcommercially available systems. The system of the present inventiondistributes 75 amperes along one edge of the daughter card through 92equi-current compliant pins with less than about 10 millivolts totalvoltage drop from the system bus to the most blade-remote daughter cardsite adjacent to the card edge bus. Return current is collected by theproximate bus with similar performance. Identical capability is providedby the card edge bus system affixed to the opposite edge of the daughtercard. Where only one bus bar assembly is desired, an electrically inertor dummy rail member is applied to the opposite side edge in lieu of abus bar assembly thereat.

The bus bar assembly of the present invention provides a pair ofsomewhat thin bus members opposing each other along facing majorsurfaces separated by a thin layer of insulation and providing a lowimpedance advantage along the daughter card edge. The thin nature of thebus members in the direction of the card array presents a relatively lowprofile module which permits forced air flow between adjacent cards fromabove and below the array. While the bus bars could be mounted to thecard edge by conventional means such as bolts, the array of compliantpin terminals disclosed provide excellent mechanical mounting as well asexcellent electrical connections at a substantial plurality of separatebut closely spaced sites.

In the present invention, the bus assembly with its plurality ofcompliant pin terminals is assuredly but easily mounted to a card edge,and thus to real estate of the daughter card previously electricallyunused. By compliant pin terminals entering the daughter card from acommon side (the reference surface), the bus bars and the bus bar moduleare therefore essentially independent of substantial variations in cardthickness. Since the card edge connectors along the rear edge are alsomounted with respect to the same reference surface, and the rail of theinsulator is positioned with respect to the reference surface,consequently the card cage adapted for the power distribution system ofthe present invention is also essentially independent of such cardthickness variations, and can be standardized.

The sequence of power first, signal last is achieved without interferingwith precision alignability of the signal connectors on the rear edgewith the backplane connectors while the card is under power, and thereturn power circuit engages before the source power circuit. Precisionalignability is attained by reason of float mounted power contacts ofthe card cage bussing system at each card location The present inventionresults in only minimal voltage drop from the card cage bussing systemto the card's power circuitry.

Variations and modifications may be made to the preferred embodimentdisclosed hereinabove, within the spirit of the invention and the scopeof the claims.

What is claimed is:
 1. A bussing means for a daughter card insertableinto a card cage, for transmitting and distributing electrical power tothe card from corresponding power bussing means of the card cage uponinsertion of the card into the card cage at a selected location,comprising:an assembly of a source bus member and a return bus memberhaving elongated body sections secured together about insulative meanstherebetween, said assembly adapted and oriented to extend along atleast a substantial portion of a card edge, each said bus memberincluding at least one flange section depending from said body sectionthereof, at least one said flange section including a plurality ofcontact means corresponding to a like plurality of contact means of adaughter card along an edge thereof, each said bus member furtherincluding a contact means matable with a corresponding contact means ofsource and return ones of said corresponding power bussing means of saidcard cage upon insertion of said card into said card cage, and said busmembers having an insulative covering thereover exposing at least saidplurality of contact means for electrical engagement with said cardcontact means and exposing said contact means, defining a bus barassembly to be mounted along at least one of an upper edge and a loweredge of a said daughter card.
 2. A bussing means as set forth in claim 1wherein each said flange section is adapted to extend a selecteddistance inward along a major surface of a said card from a said one ofsaid upper edge and said lower edge thereof to extend over power circuitmeans of said card intersected by an array of through-holes, and eachsaid flange section includes a corresponding array of pin terminalsextending normally therefrom toward said array of through-holes, wherebysaid pin terminals are receivable into respective said through-holes toestablish a plurality of electrical connections with said card powercircuit means upon mounting of said bus bar assembly to said card.
 3. Abussing means as set forth in claim 2 wherein said pin terminals arecompliant pin terminals adapted to self-retain within said through-holeswith substantial gripping force to resist withdrawal therefrom, wherebysaid compliant pin terminals define a means for mounting said busmembers to said card.
 4. A bussing means as set forth in claim 3 whereinsaid compliant pin terminals are disposed in at least a pair of rows. 5.A bussing means as set forth in claim 4 wherein said compliant pinterminals of each said row are fabricated on carrier strips andmaintained thereon during assembly to respective said flange sectionsand during assembly of said bus bar assembly to a said card edge,thereby defining stop means for insertion of said compliant pinterminals into said apertures of said flange sections to a selecteddepth, and insertion of said compliant pin terminals into saidthrough-holes to a second selected depth and thereafter commoning thepin terminals of each said row.
 6. A bussing means as set forth in claim2 wherein each said bus member includes a plurality of said flangesections of selected length alternating with flange-receiving recessesof lengths just larger than said selected length, and said flangesections of one said bus member are offset with said flange sections ofthe other said bus member to correspond with said flange-receivingrecesses of said one bus member, whereby said bus members are securabletogether with said respective flange sections becoming interspacedbetween said flange sections of each other.
 7. A bussing means as setforth in claim 6 wherein said flange sections are offset transverselywith respect to the longitudinal axis of said bus member and toward theother said bus member during assembly a distance about equal to one-halfthe thickness of a said flange section, whereby upon said bus membersbeing secured together said flange sections are disposed in a commonaligned row such that card-facing surfaces thereof essentially define acommon plane.
 8. A bussing means as set forth in claim 6 wherein a smallspacing is defined between facing edge surface of adjacent ones of saidflange sections of said one and said other bus member, therebyelectrically insulating said flange sections from each other.
 9. Abussing means as set forth in claim 8 wherein said insulative coveringhas a constant cross-section therealong enabling fabrication thereof byextrusion, and said extruded insulative covering is securable about saidbus members by deforming a portion thereof extending over card-remotesurfaces of said flange sections into at least one said small spacingbetween adjacent ones of said flange sections, after insertion over saidbus members from a common end thereof.
 10. A bussing means as set forthin claim 1 wherein said insulative covering has a constant cross-sectiontherealong enabling fabrication thereof by extrusion.
 11. A bussingmeans as set forth in claim 10 wherein said insulative covering includesa rail for following a complementary guide channel of a guide means ofsaid card cage during insertion of said card into said card cage.
 12. Abussing means as set forth in claim 11 wherein said rail of saidinsulative covering further includes a portion therealong extendingoutwardly and being offset laterally from the median of said rail todefine a polarizing means corresponding to complementary polarizingmeans of a corresponding said guide member of said card cage, wherebyupon said bus bar assembly being mounted to said one of said upper andlower edges of a said daughter card, and said daughter card includingrail means along the other of said upper and lower edges correspondingto an opposing said guide member, said offset rail portion requiresproper orientation of a said card module prior to insertion into saidcard cage when said opposing guide member does not include a saidcomplementary polarizing means diagonally opposed to that of saidcorresponding guide member, thereby defining a polarization meansdisallowing daughter card insertion in an inverted orientation into andbetween said corresponding guide member and said opposing guide member.13. A bussing means as set forth in claim 11 wherein said rail has aparticular cross-sectional shape selected to complement thecross-sectional shape of said guide channel of the particular one ofsaid guide members into which said rail is to be inserted duringappropriate card insertion into said card cage, said particularcross-sectional shape further selected not to complement an othercross-sectional shape of a said guide channel of an opposing one of saidguide members associated with said daughter card, thereby defining apolarization means disallowing daughter card insertion in an invertedorientation into and between said particular guide member and saidopposing guide member.
 14. A bussing means as set forth in claim 1wherein an insulative end cover is mountable to a said card along aforward edge thereof proximate said one of said upper edge and saidlower edge, to include a portion coextending along an end of said busbar assembly for insulation of end surfaces of said bus members.